Is it possible to change the axes/part that the vortex forcefield is attracting?
Well, there is 2 ways to do this.
In the particle settings, go to rotation and uncheck dynamic. This means they all point in one direction.
But I doubt this will give you what you want, its just a quick fix.
The way I find works best is to just take your instance object, enter edit mode, and mess with the rotation and location until you find something that is decent. Rotation works better than location. For it to work, you have to be in edit mode when editing transforms.